How to render the black lines at the edges of an object?
It is called Freestyle Line style

Add a base color and in the Render -> Freestyle (tick mark)



If you want to change the color of the stroke (line)
Under Render Layer -> Freestyle Line style -> color -> Base color (change the color from black to any color)



Hit F12 to render after finishing the render wait a second to complete the Freestyle Line style render and you can see a outline of the color.